Life Cycle Inventory Comparison of Biodiesel and Petroleum Diesel Fuels Shih-Hao Pang and H. Christopher Frey Department of Civil, Construction, & Environmental Engineering North Carolina State University Raleigh, NC 27695 Prepared for: Emerging Fuels Issues Workshop Atlanta, GA December 6, 2006
Objectives • The objective of this study is to predict energy use and emissions of construction vehicles for the fuel life cycle and the vehicle itself. The key questions are: • What are the best estimates of fossil energy use and emissions for petroleum diesel and biodiesel life cycle? • What are the implications of using biodiesel fuel with respect to the spatial distribution of emissions?
Background • Biodiesel is a domestic, renewable fuel for diesel engines derived from fats and oils such as soybeans or animal fats • Biodiesel is produced by a chemical process that removes glycerin from the oil • Raw vegetable oil is not biodiesel • Comparing biodiesel to petroleum diesel, dynamometer test results indicate (EPA 2002): • Lower emission rates for particulate matter (PM), volatile organic compounds (VOC) and carbon monoxide (CO) • Higher emission rates for NOx
U.S. Biodiesel Consumption Source: Soy Stat 2005
Solvent Extraction in Biodiesel LCI • Soybean oil extraction is the major source of VOC emissions in the biodiesel life cycle inventory. • In November 2004, the final rule of National Emission Standards for Hazardous Air Pollutants of solvent extraction process was promulgated, which reduces allowable VOC emissions levels from new vegetable oil production facilities VOC Emission (gal/ton soybean) Old Soyoil Plant New Soyoil Plant
Tailpipe Emissions for Comparison of B20 Biodiesel vs. Petroleum Diesel Reduction in tailpipe emissions from use of biodiesel fuels versus petroleum diesel • EPA (2002) – Engine Dynamometer Average percent changes for engine dynamometer test of 43 heavy-duty diesel engine • Frey and Kim (2006) – In-Use Measurement Average percent changes for in-use measurements of 12 dump trucks
Tailpipe Emissions for Comparison of B20 Biodiesel vs. Petroleum Diesel
Distribution of Energy Use and Emissions Petroleum Diesel Life Cycle 16% 15% 3% 4% 4% 3% Percentage of Total
Distribution of Energy Use and Emissions B20 Biodiesel Life Cycle (Old Soybean Oil Plant with Engine Dynamometer Data) 21% 20% 5% 8% 10% 46% Percentage of Total
Distribution of Energy Use and Emissions B20 Biodiesel Life Cycle (New Soybean Oil Plant with Engine Dynamometer Data) 22% 20% 5% 6% 8% 27% Percentage of Total
Life Cycle Energy Use The total energy includes the heating value of fuel itself and process energy. Biodiesel is considered as renewable energy. 0. 07% of diesel transport fuel is biodiesel. 17% Energy (103 Btu/gallon) 63% 99.9% 83% 37% Reduction in LCI Fossil Energy: B20: - 9.1% B100: - 45.3%
Cumulative Frequency of Emission Reduction (%) of B20 LCI Compared to Petroleum Diesel LCI CO VOC NOx PM New Soyoil Plant and Engine Dynamometer Data New Soyoil Plant and In-use Measurement Data
Implications of Using Biodiesel with Respect to Spatial Distribution of Emissions • Tailpipe emissions of PM, CO and THC decrease when using biodiesel. • Although some engine dynamometer data suggest a small increase in the emission rate of nitrogen oxides (NOx), other data suggest that the overall average change in NOx emissions may be cycle-dependent. Tailpipe emissions of NOx may decrease in some cases. • It is possible to reduce urban emissions of PM, CO, and THC by using B20. • However, fuel cycle emissions may increase in Midwest (and other agricultural) states because of biodiesel production.
Conclusion • Life cycle energy use of biodiesel is higher than petroleum diesel, but less fossil energy is used. • B20 has lower life cycle emissions of VOC, CO, PM10 and NOx based on a new soyoil plant and in-use measurement data which may be cycle-dependent. • Using biodiesel may decrease tailpipe emissions in urban areas. However, fuel cycle emissions may increase in Midwestern states. • Biodiesel is a promising alternative fuel for diesel, but there are some environmental trade-offs.
Acknowledgement Sponsored by National Science Foundation Disclaimer This material is based upon work supported by the National Science Foundation under Grant No. 0327731. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.